ELI5: Explain ISIS, please.

This is a terrible question, I'm sorry. But all I know is that they are groups of people who kill people. (This probably isn't in the right subreddit, but I don't know which one to put it under.) Who are they? What have they done so far? Where are they? Can they be stopped? Can you tell me some stories from the news that they have done?

They go by many varying names, but Islamic State (IS) is the simplest so I'll just use that. AFAIK, IS are a radical Islamist organization made up of many groups. I'm fairly sure they contain some splinter groups from Al Qaeda, but the majority are either former Baathists (members of Saddam Hussein's regime) who were excluded from government after Saddam's defeat, or Sunni Muslims from Kurdistan (Northern Iraq). To be brief, all these groups have beef with the Iraqi government for various reasons.

So far, IS occupies large areas of northern Iraq and Iraqi Kurdistan, and also has branches stretching into eastern Syria. They delivered several crushing defeats to the Iraqi army to take this territory. When it comes to news stories, well, where to start? Multiple decapitations of kidnapped foreign journalists, mostly Western; beheading and crucifying those in their lands who refuse to convert their faith and swear loyalty; the torture and burning alive of captured soldiers; etc.

Can they be stopped? Certainly. They aren't massive in number but they contain well-trained fighters and are armed with tanks and weapons looted from the retreating Iraqi army. Airstrikes alone won't defeat them. It will require a concerted ground offensive, and the West is unlikely to play any major role in any such operations.

Most of my info comes from what I see in the media, but I'm currently in my second year of a War Studies degree and IS obviously comes up often in discussion. So if you have any more questions, feel free to ask.

It is an acronym meaning Islamic State in Iraq and Syria; other names for them are ISIL (Islamic State in Iraq and the Levant), Daesh (apparently an Arabic acronym which they hate) and IS (their preferred nomenclature, standing simply for Islamic State).

They are an insurgent/terrorist group that is descended from al-Qaeda in Iraq, a group that arose to fight the Coalition troops in Iraq post-Gulf War 2 that spread to fight in the Syrian Civil War against Bashar al-Asad's regime where they drew various other insurgent groups under their banner.

They are hardline Salafist Sunni Muslims whose main hatred is for the Shia whom they view as apostates (al-Asad is from a group that is a sub-branch of the Shia branch of Islam) which is why Iran and Hezbollah are fighting them.

Their ultimate aim is to create a new Caliphate, or Islamic state, throughout all Muslim lands. So far they hold a large contiguous area within Iraq and Syria.

They originally came to notice fighting the majority Shia Iraqi regime/government of Nouri al-Maliki in Sunni dominated regions of Iraq, during which battles they beat the Iraqi Security Forces convincingly, capturing large amounts of military equipment (much of it US donated to Iraq) and huge swathes of territory including major cities such as Mosul and areas that hold large oil reserves.

They also attacked regions where religious minorities such as the Yazidi live. Everywhere they have captured they have inflicted atrocities on non-Sunni Muslims.

Their expansion was stopped by the Kurds who provided the only effective resistance thus far. It was Kurdish fighters who recently defeated them in Kobane, the siege of which city was a long running news story.

They are notorious for beheading Western hostages and now burning prisoners including the Jordanian F-16 pilot recently in the news.

Recently they have suffered heavy losses and military defeats due to Western air power support. The Iraqi Security Forces are currently gearing up to attack again soon.

Of course they can be beaten, but it will require significant time and resources as well as a plan for what follows. Simply defeating them militarily will leave the tensions in the region, both religious and ethnic, extant and inevitably another similar fight will break out without a political solution to accompany the military effort.

In addition to the posts already made it should be pointed out that they see themselves as playing a role in the apocalypse (they see themselves as the good guys for strict adherence to sharia law). Their leader is able to achieve a lot of recruitment because he's been declared a caliphate. Religiously those who follow sharia and don't swear him allegiance are considered to heretics and subject to appropriate disciplinary action by those loyal to the caliphate. I submit the following for the basis of my understanding. http://www.theatlantic.com/features/archive/2015/02/what-isis-really-wants/384980/

Islamic State of Iraq and the Levant (ISIL) or Islamic State in Iraq and Syria (ISIS) [4] or Islamic State[5][6] is a jihadist militant group in Iraq and Syria. It is influenced by the Wahhabi version of Islam.[7][8] It claims the status of independent state for the territories under its control in Iraq and Syria. It is opposed to Shiism and has been described as Shiaphobic.[9][10]

The group was started in the early years of the Iraq War and associated itself with al-Qaeda in 2004. ISIL was composed of different insurgent groups. Its aim was to establish a caliphate in the Sunni majority regions of Iraq, later expanding this to include Syria.[11] In February 2014, after an eight-month power struggle, al-Qaeda cut all ties with ISIL.[12]

I'm pretty sure someone will give you a detailed explanation, I'm just here to share the fact that ISIS finds it perfectly rational to behead smokers because smoking is "slow suicide" and suicide is forbidden by Sharia Law.

Oh, and they're so extremist and crazy even Al Qaeda doesn't want to be associated with them.

While I am by no means an expert on the subject, I do follow the news quite religiously, so I'll do my best. The Islamic State of Iraq and al-Sham (ISIS, also sometimes called ISIL for Islamic State of Iraq and the Levant) is a terrorist organization that has a current end-goal of creating an area in the Middle East owned and governed by Muslims, using Sharia Law. They currently own land in much of Iraq and Syria, and have killed many people in order to do so. I am unfamiliar with their history, but they have been around since 1999, with various goals throughout. It is my understanding that a majority of ISIS (or ISIL) is made up of a minority of ultra-conservative Muslims who feel marginalized by their fellow believers. It is also my understanding that they can be stopped, but momentum against them is still growing, and it is my opinion that many governments need to treat the situation more seriously.

The war mongers who actually run this planet need us to have someone to hate and fear, so that we will buy their wares. They supply arms etc. to both sides of the battles so they never lose. Religious extremists are easy to exploit, because they're dumbasses.